346 M. F. Kohlrausch on the Absolute Value of the 



lims. in length, 14 millims. in thickness, and each of them 

 weighs nearly 200 grms. The inner one had about 45 million 

 units of magnetism, the outer one 2 millions fewer. (It follows 

 from this that the local influence on the inductor, which was 

 about 5500 millims. distant, amounted at most to the 100,000th 

 part of the terrestrial magnetism.) 



The magnets lie with two grooves in the double forks of a 

 stirrup, which hangs to a torsion-circle with a mirror, and half 

 encircles the multiplier. The upper horizontal part of the stir- 

 rup is extended, and bears at its ends, each at a distance of 100 

 millims. from the centre, two small vertical rods, which are in- 

 tended to support two cylindrical brass weights perforated axially, 

 for the determination of the moment of inertia. The weights 

 are each 28 millims. in diameter, and have each a mass of 100 

 grms. After removing the upper magnet, a small rod may be 

 fastened in the centre of the stirrup, and the weights may be 

 placed on it on the top of each other. By a small sliding weight, 

 not seen in the figure, the centre of gravity is so regulated that 

 the superposition of the weights does not alter its position. 



The whole was suspended by a steel wire, about J millim. in 

 thickness and 2*7 millims. in length, from a beam in the roof, 

 and was carefully protected against currents of air by a box with 

 glass plates in the sides. 



Moment of Inertia of the pair of Needles. 



Mass of the weights together . . =199970 mgrras. 



External semidiameter of the same . 13*95 millims. 



Internal semidiameter of the same . 0*85 millim. 

 Hence the moment of inertia of the two together in reference to 

 their axis, 



= 199970 ,7 =19500000 millim. 2 milligrm. 



Distance of the centre of the weights from each other when 

 they were put on the extreme projections, 



199-824 millims. at 17°. 



Hence common moment of inertia in the latter position, re- 

 ferred to the suspension wire at 17°, 



19500000 + 199970 .99*912 2 = 2015700000 millim. 2 mgrm., 



and at 22°-5, 2016100000 



The times of oscillation corresponding to each other were 

 always measured with nearly equal arcs, so that a reduction is 

 unnecessary. Where there are two observations with the same 

 load, one was always made before and the other after the second 

 loading. 



